In some vehicles, electrically motorized wheels propel or retard the vehicle. In particular a large horsepower diesel engine may be used with an alternator, a traction inverter, and wheel drive assemblies housed within the rear tires of the vehicle. In operation, a diesel engine drives an alternator, which powers the traction inverter. The traction inverter includes semiconductor power switches that commutate the alternator output current to provide electrical power to electric drive motors, e.g., AC traction motors, of the wheel drive assemblies, which transform the electrical power back into mechanical power to drive the wheels and propel the vehicle.
Many such vehicles also require cooling systems for the engine and other components in order to maintain temperatures below maximum operating thresholds of such components. For example, a radiator and fan may be utilized to cool the engine. The radiator is typically situated behind a grille, which permits air to flow therethrough and to the radiator. The air contacts and cools the radiator fins, which in turn cool the circulating radiator fluid that cools the engine. Additional fans and air inlets (with or without a radiator) may be utilized to provide cooling for other components of the vehicle.
The configuration and operation of existing systems, however, may adversely affect fuel economy of the vehicle, particularly in cold weather or at higher vehicle speeds. In particular, existing systems typically do not allow for airflow horsepower to be reduced in operating modes that require reduced or no cooling due to direct coupling of the fan to the alternator and engine. In particular, operation of the fan in such modes requires the continuing consumption of fuel, even though no cooling may be needed. Moreover, as the velocity of a vehicle increases, the amount of airflow through the grill and into the engine compartment increases, which slows the vehicle and makes the engine work harder. The additional airflow through the grille at higher vehicle speeds can therefore detrimental to fuel economy. In particular, as vehicle velocity increases, the amount of aerodynamic drag increases as a result of the increased airflow into the engine compartment. As aerodynamic drag increases, more energy is required to move the vehicle.
In view of the above, there may be a need for a system and method which differ from those that are currently available.